1. Field of the Invention
This invention relates to a tilt and trim arrangement for a marine propulsion, and more particularly to an improved tilt and trim arrangement that is reinforced against external force while remaining compact.
2. Description of Related Art
Marine outboard drives, i.e., both outboard motors and the outboard drive sections of inboard motors, have drive units mounted on an associated watercraft by a tilt and trim arrangement or bracket assembly which comprises a swivel bracket and a clamping bracket. The swivel bracket carries the outboard drive unit for pivotal movement about a generally vertically extending steering axis. The clamping bracket, in turn, is affixed to the associated watercraft and supports the swivel bracket for pivotal movement about a generally horizontally extending tilt axis.
The bracket assembly includes a hydraulic tilt device disposed between the swivel bracket and the clamping bracket so that the swivel bracket is tilted up or down relative to the clamping bracket. The hydraulic tilt device is, for example, a compound tilt and trim cylinder assembly.
The hydraulic tilt device includes a cylinder assembly having a cylinder housing which defines a cavity therein. A piston is slidably supported in the cavity. A piston rod is affixed to the piston and extends beyond the cavity. The swivel bracket has a pair of ribs spaced apart transversely from each other and a pivot pin extends between them. The piston rod is affixed on the pivot pin for pivotal movement. Meanwhile, the clamping bracket also has a pair of ribs spaced apart transversely from each other and another pivot pin extends between them. The cylinder housing is affixed on this pivot pin for pivotal movement. A powering assembly is provided for pressurizing working fluid in the cavity of the cylinder housing. The powering assembly includes an electric motor, a hydraulic pump and a reservoir, all of which are relatively bulky. With the reciprocal movement of the piston in the cavity of the cylinder housing, the piston rod extends from or contracts into the housing and the drive unit, thereby, is tilted up or down in a certain range.
Recently, outboard motors are inclined to have larger engines than before because more powerful and high speed propulsions are desired. This trend necessarily invites large sized drive units to support such large engines which are quite heavy as well as unwieldy. In addition, these outboard motors produce large thrust force. The bracket assembly accordingly must support a heavy drive unit and receive such a large thrust force. The ribs and hydraulic tilt assembly need to be bigger and have more sufficient rigidity in order to withstand the increased weight of the drive and the increased spacing necessary to receive the larger powering assembly. In fact, the bulky cylinder housing and powering assembly are likely to cause a problem as to how they are disposed in a limited space between the rigid ribs.
Some conventional bracket assemblies have a cylinder assembly and a powering assembly positioned side-by-side to each other. However, a cylinder housing of this cylinder assembly must be off-centered and hence produces a torque upon the ribs when the cylinder extends and contracts. Thus, the ribs require reinforcement and, if reinforced, they are larger, which further exacerbates the arrangement of the cylinder and powering assembly between the clamping and swivel brackets.
Other conventional bracket assemblies have a cylinder housing spaced widely from the swivel bracket. This arrangement, however, does not present a compact bracket assembly.